(DEFUN READB (U) 
       (COND ((EQ (CAR U) 'LP) (CAR (READA (CDR U) NIL)))
	     (T (CAR U))))

(DEFUN READA (U L) 
       (COND ((NULL U) (CONS (REV1 L 'ERROR) NIL))
	     ((EQ (CAR U) 'RP) (CONS (REVERSE L) (CDR U)))
	     ((EQ (CAR U) 'LP)
	      ((LAMBDA (W) (READA (CDR W) (CONS (CAR W) L)))
	       (READA (CDR U) NIL)))
	     ((EQ (CAR U) 'DOT)
	      ((LAMBDA (W) (CONS (REV1 L (CAAR W)) (CDR W)))
	       (READA (CDR U) NIL)))
	     (T (READA (CDR U) (CONS (CAR U) L)))))

(DEFUN PRINA (E L) 
       (COND ((ATOM E) (CONS E L))
	     (T (CONS 'LP
		      (PRINA (CAR E)
			     (CONS 'DOT
				   (PRINA (CDR E)
					  (CONS 'RP L))))))))

(DEFUN PRINB (E L) 
       (COND ((ATOM E) (CONS E L))
	     (T (CONS 'LP
		      (COND ((NULL (CDR E))
			     (PRINB (CAR E) (CONS 'RP L)))
			    ((ATOM (CDR E))
			     (PRINB (CAR E)
				    (CONS 'DOT
					  (CONS (CDR E)
						(CONS 'RP
						      L)))))
			    (T (PRINB (CAR E)
				      (CDR (PRINB (CDR E) L)))))))))

(DEFUN REV1 (U V) 
       (COND ((NULL U) V) (T (REV1 (CDR U) (CONS (CAR U) V)))))